A vane-type valve-timing-adjusting-device, which drives the cam shaft via a timing pulley or a chain sprocket which rotates in synchronism with the engine crank shaft to control operation of the air intake valve and the exhaust valve in accordance with the phase difference between the timing pulley or the chain sprocket and the cam shaft, is well known. Such vane-type valve-timing-adjusting devices are disclosed in Japanese Patent Unexamined publication Hei 1-92504, Japanese Utility Model Unexamined Publication Hei 2-50105, Japanese Patent Unexamined Publication Hei 5-106412, and Japanese Patent Unexamined Publication Hei 5-214907. Such kind of vane-type valve-timing-adjusting devices has a pressure chamber disposed at an inner periphery of the timing pulley and a vane disposed in the pressure chamber. The vane is rotated relative to the cam shaft by oil pressure, for instance, in the advancing or retarding direction to control the valve timing of the intake valve and the exhaust valve.
However, since the circumferential width of the vane of the above conventional vane-type valve-timing-adjusting device is so small, it is difficult to seal gaps between an advancing chamber and a retarding chamber by the circumferential edge of the vane. For instance, when the vane is rotated by the pressure difference between the retarding chamber and the advancing chamber, oil may leak between the two chambers with the result that the pressure difference between the retarding chamber and the advancing chamber may not become a predetermined value and that accurate control of the intake and exhaust valves may not be carried out.
Japanese Patent Unexamined Publications Hei 5-106412 and Hei 5-214907 disclose devices in which each vane has lobes on the outer periphery thereof and accommodates two check valves inside thereof. However, the check valve must endure the centrifugal force caused by rotation of the cam shaft. In addition, since the vane of the above conventional device accommodates the check valves at the central portion thereof, the size of the lobe is limited and, therefore, cannot have sufficient area to receive the oil pressure, resulting in increasing the size of the device.